Layout of mirrored databases across different servers for failover

Abstract

A plurality of data centers each having a plurality of servers. When there is a failure on a data center, the load for the failed portion of the data center is distributed over all the remaining servers locally, or remotely, based on the magnitude of the failure.

What is claimed is: 
     
         1 . A computer-implemented method of operating a data storage system, implemented by a computer with a processor, comprising:
 serving primary and secondary copies of at least six different availability groups using at least a first data store server, a second data store server and a third data store server;   detecting a failure of the first data store server; and   operating according to fail over operation by balancing a load for serving the primary copies of the availability groups served using the first data store server among the at least second data store server and third data store server.   
     
     
         2 . The computer-implemented method of  claim 1  and further comprising:
 assigning the primary and secondary copies of the at least six different availability groups to the at least first, second and third data store servers according to an initial configuration. 
 
     
     
         3 . The computer-implemented method of  claim 2  wherein assigning the primary and secondary copies of the at least six different availability groups to the at least first, second and third data store servers according to an initial configuration, comprises:
 load balancing the serving of the primary and secondary copies of the at least six different availability groups across the at least first, second and third data store servers. 
 
     
     
         4 . The computer-implemented method of  claim 3  wherein load balancing, comprises:
 assigning service of primary copies of two different availability groups and secondary copies of two more different availability groups to each data store server in the initial configuration. 
 
     
     
         5 . The computer-implemented method of  claim 3  and further comprising:
 detecting a remedy of the failure of the first data store server; and 
 restoring service of the primary and secondary copies of the at least six different availability groups to the at least first, second and third data store servers according to the initial configuration. 
 
     
     
         6 . The computer-implemented method of  claim 1  wherein each availability group includes a plurality of different databases that are migrated together for fail over operation. 
     
     
         7 . The computer-implemented method of  claim 6  wherein the data storage system includes at least first and second data centers and wherein detecting a failure comprises:
 detecting the failure on the first data center. 
 
     
     
         8 . The computer-implemented method of  claim 7  and further comprising:
 after detecting a failure on the first data center, determining whether the failure has a magnitude that meets a remote fail over threshold; and 
 if so, operating according to the fail over operation comprises operating according to a remote fail over operation by distributing the load of the primary and secondary copies of the availability groups among the data store servers on at least the second data center in the data storage system to load balance the data store servers on at least the second data center. 
 
     
     
         9 . The computer-implemented method of  claim 8  wherein determining whether the failure has a magnitude that meets a remote fail over threshold, comprises:
 determining whether a number of failed data store servers on the first data center meets a threshold number. 
 
     
     
         10 . The computer-implemented method of  claim 9  wherein the data storage system includes at least the second data center and a third data center, and wherein distributing the load of the primary and secondary copies of the availability groups among the data store servers on at least a second data center in the data storage system, comprises:
 distributing the load of the primary and secondary copies of the availability groups among the data store servers on at least the second and third data centers in the data storage system. 
 
     
     
         11 . The computer-implemented method of  claim 9  and further comprising:
 assigning the primary and secondary copies of the at least six different availability groups, and first and second asynchronous copies of the at least six different availability groups to the data store servers on the at least first and second data centers according to an initial configuration. 
 
     
     
         12 . The computer-implemented method of  claim 11  wherein operating according to the remote fail over operation comprises:
 assigning only the first and second asynchronous copies of the at least six different availability groups to the data store servers on the first data center. 
 
     
     
         13 . The computer-implemented method of  claim 12  and further comprising:
 detecting a remedy of the failure of the first data center; and 
 restoring service of the primary and secondary copies of the at least six different availability groups to the data store servers on the at least first and second data centers according to the initial configuration 
 
     
     
         14 . A data storage system, comprising:
 a first data center, comprising:   at least a first data store server, a second data store server, and a third data store server, each serving primary and secondary copies of at least six different availability groups according to an initial, load balanced, configuration;   a second data center, comprising:
 at least a fourth data store server, a fifth data store server, and a sixth data store server, each serving primary and secondary copies of at least six additional availability groups according to an initial, load balanced, configuration; and 
 at least one computer processor that detects failure of at least one of the data store servers in the data storage system and identifies it as a failed data store server and begins fail over operation by transferring service of at least the primary copies of the availability groups assigned to the failed data store servers, in a load balanced way, either to a remainder of the data store servers on a same data center as the failed data store server or to a set of data store servers on at least the second data center. 
   
     
     
         15 . The data storage system of  claim 14  wherein the at least one computer processor detects that the failure has been fixed, and transfers service of at least the primary copies of the availability groups back to the initial, load balanced, configuration. 
     
     
         16 . The data storage system of  claim 15  wherein the at least one processor detects a magnitude of the failover and assigns at least the primary copies of the availability groups assigned to the failed data store servers, in a load balanced way, either to a remainder of the data store servers on a same data center as the failed data store server or to a set of data store servers on at least the second data center based on the magnitude of the failure. 
     
     
         17 . The data storage system of  claim 16  wherein, when the at least one processor assigns at least the primary copies of the availability groups assigned to the failed data store servers, in a load balanced way, to the set of data store servers on at least the second data center, the at least one processor assigns only asynchronous copies of the availability groups to data store servers on the same data center as the failed data store server. 
     
     
         18 . The data storage system of  claim 17  wherein each availability group includes a plurality of different databases that are migrated together for fail over operation. 
     
     
         19 . A computer-implemented method of operating a data storage system, implemented by a computer with a processor, comprising:
 serving primary, secondary and first and second asynchronous copies of at least twelve different availability groups, according to a normal configuration, using at least a first data center with a first data store server, a second data store server and a third data store server, and a second data center with a fourth data store server, a fifth data store server and a sixth data store server, each availability group including a plurality of different databases that are migrated together for fail over operation;   detecting a failure, having a magnitude, of at least one of the data store servers;   performing a selected fail over operation comprising one of a remote fail over or a local fail over, based on the magnitude of the failure;   operating according to the selected fail over operation, comprising:
 when the selected fail over operation comprises the local fail over operation, balancing a load for serving the primary and secondary copies of the availability groups served using the at least one failed data store server among a remainder of the data store servers in the data center of the at least one failed data store server; and 
 when the selected fail over operation comprises the remote fail over operation, balancing a load for serving the primary and secondary copies of the availability groups served using the at least one failed data store server among a the data store servers in the data center that does not include the at least one failed data store server; 
 detecting a remedy of the failure; and 
 performing a fail back operation comprising returning to the normal configuration. 
   
     
     
         20 . The computer-implemented method of  claim 19  wherein when the selected fail over operation comprises the remote fail over operation, assigning only asynchronous copies of the at least twelve different availability groups to the data center that includes the at least one failed data store server.